Increasing demand for intelligent packaging materials are "materials and articles that monitor the condition of packaged food or the environment surrounding the food". Curcumin, as well as the extract of grape peel, have been examined as a pH indicator used in relation to their ability to monitor the deterioration of the quality and freshness of fish. These two substances were characterized by sensitivity to volatile chemicals corresponding to spoilage of food products. The colorimetric sensor with curcumin very clearly changed color from yellow to orange during the deterioration of the quality and freshness of cod. The authors proposed curcumin and grape skin extract as effective colorimetric indicators of freshness of food in an intelligent package.